The present invention relates to a method useful in reducing the fluorescence in secondary fibers. Therefore, the present invention finds particular application in a recycling process for used paper which contains fluorescent dye. More specifically, the present invention comprises a method which more effectively employs ozone in reducing the fluorescence of pulp fibers, and especially deinked pulp fibers.
Environmental considerations have generated a growing trend toward increased utilization of recycled fibers. Recycled fiber furnishes, which are generally obtained through the recycle of used or waste paper, e.g., newspaper, often contain fluorescent dyes which are believed to be possible carcinogens. Food board manufacturers, responding to environmentally driven pressures, would like to include secondary fibers in their furnish. However, it is unacceptable to have possible carcinogens in contact with food. Conventional fiber treatment methods, unfortunately, have little defluorescence activity with regard to fluorescent dye containing paper.
One possible alternative in order to more effectively reduce the fluorescence of recycled fibers is to treat recycled pulp with chemical quenchers. It should be noted that quenchers are expensive, however, and have no bleaching effect. Therefore, the pulp must be bleached and separately treated with the quencher. Some bleaching chemicals, such as hydrogen peroxide, can actually increase fluorescence.
The use of chlorine compounds can be considered for the neutralization of fluorescent dyes as chlorine compounds do bleach and attack fluorescent dyes. However, new environmental regulations require that the level of organochlorine compounds in mill effluents be reduced to a minimum.
The use of ozone in the treatment of recycled fibrous material for different reasons is known. For example, Japanese patent application 61-192381 concerns a process for waste treatment which employs ozone. Ozone is infiltrated through the fibrous waste material in order to remove residual butyric acid and fatty acids and for the purpose of deodorization. The fibrous material can then be used for the fabrication of fiber sheets.
Similarly, in German patent application 3001862, published Jul. 23, 1981, there is disclosed a process for the production of a raw material useful for making paper from waste paper. In the process, the waste paper itself is treated with a gaseous disinfecting agent, such as ozone. Subsequent to the treatment, the waste paper is subjected to a recycling procedure, for example, involving solvent treatment and fibrillation. The waste paper, due to its contact with household garbage, is generally strongly contaminated with bacteria and microorganisms. The use of the ozone disinfectant agent destroys the bacteria and microorganisms to permit odor free, safe subsequent handling of the paper.
The use of ozone as a bleaching agent for pulp is also known. See, for example, "Bleaching Deinked Pulp with Ozone" by Jack Kogan and Michel Muguet, Progress and Paper Recycling, November, 1992.
The use of ozone for treating used paper is also disclosed in Japanese Kokai 3199477. The process described, however, uses the ozone to decolorize and defluoresce the used paper. The process involves the reaction of ozone with the used paper in a slurry dispersion comprised of at least 20% water.
Thus, ozone is known to be useful in processes treating recycled paper, and is known to reduce fluorescence in an environmentally friendly manner. Greater expediency and efficiency, however, with regard to the use of ozone in the treatment of paper, and in particular in overcoming the problems of extinguishing fluorescence, would be welcome in the paper industry. For to render such a defluorescence process more effective and efficient would make the process more desirable and aid in the use of recycled fibers in applications where heretofore they have not been used.
Accordingly, one object of the present invention is to provide a novel process for reducing fluorescence in fibers such as secondary fibers.
Yet another object of the present invention is to provide a cost effective and efficient process for treating recycled pulp containing fluorescent dye.
These and other objects of the present invention will become apparent upon a review of the following specification, the figures of the drawing, and the claims appended thereto.